DISTRIBUTION OF SAPROPHYTIC FUNGI ANTAGONISTIC TO FUSARIUM-CULMORUM IN 2 DIFFERENTLY CULTIVATED FIELD SOILS, WITH SPECIAL EMPHASIS ON THE GENUS FUSARIUM

The purposes of the present study were to search for antagonistic fung i to control seed-borne diseases of cereals caused by Fusarium culmoru m (W.G.Sm) Sacc. and to use these results to compare the distribution of non-pathogenic Fusarium spp. and other fungi antagonistic to Fusari um culmorum in soil and on straw particles in an organically and a con ventionally cultivated field. The organic farm had been cultivated acc ording to the principles of Steiner (1963) since 1952. The sites were similar with respect to climatic conditions, soil type and vegetation. There was no difference in the total number of antagonistic fungi iso lated from the two differently cultivated fields, but the results for Fusarium spp. showed effects of the actual crop as well as the croppin g system. Soil sampling over a three year period at the organically cu ltivated farm in two crops - winter wheat or a mixture of grass and cl over shouted almost twice as many species of Fusarium in the mixed cro p compared to monoculture. In mixed crop fields, the percentage of F. culmorum in relation to total isolations of fusaria was 20% in the org anically cultivated field compared with 45% in the conventionally cult ivated field. These results indicate that pathogenic fusaria may be su ppressed by antagonistic fusaria to a larger extent in the organically cultivated field than in the conventionally cultivated field. In acco rdance with this, a higher number of antagonistic fusaria was found in the organically farmed field (14) compared to three in the convention ally farmed field. This was partly a result of a higher number of isol ated fusaria and a higher number of different species of Fusarium in t he organically cultivated soil (total number of non-pathogenic fusaria was 10 in the conventionally cultivated field and 56 in the organical ly cultivated field). However, it also seems to reflect an enrichment of fusaria with antagonistic properties towards F. culmorum. Thus, the occurrence of F. culmorum was 1.7 times higher in the organically cul tivated field while the occurrence of its antagonists was 4.6 times hi gher in the organically compared with the conventionally cultivated fi eld.